Business software must deal with change! Even something as simple as a financial account changes behavior because the balance in the account changes. Of cours

Business software must deal with change! Even something as simple as a financial account changes behavior because the balance in the account changes. Of course, many business Actors never change their behavior. For example, a quarterly report to the SEC never changes although additional reports to the SEC may correct information in previous reports. Of course, you know that Factorial is an Actor that never changes behavior :-) Also, the (infinite) list of prime numbers is an Actor that never changes behavior.